This link is broken, either the page no longer exists or there is some other issue like a typo.
This is a link for the manual for the stove. I have air vents in the front loading door to allow air in above the coal in the manual it says to keep these open for coal and closed for wood.
That doesn't sound correct to me. Typically, for coal burning, the air should be entering under the coal. Any air coming in above the coal, will dampen the fire down (it won't burn as hard).
While you are there to keep an eye on things, try closing the air above the coal and open the air below the coal, with pipe damper open, if you have one.